EPO and metastatic malignant neoplasm: In turn, reduced erythropoiesis can be due to different mechanisms, which include: 1) direct bone marrow toxicity by anticancer drugs; 2) absolute deficiency of essential micronutrients (mainly, but not only, iron); 3) functional iron deficiency due to hepcidin-induced iron sequestration into macrophages; 4) impaired bone marrow response to erythropoietin (EPO) due to tumor-associated systemic inflammation; and bone marrow substitution by metastatic cancer cells (7, 8).